NY NJ PA Weather Forecasts

The step down begins

7:10 AM

This morning, the first step towards a cold and potentially very stormy pattern is unfolding.  A very strong coastal low continues to intensify off the New England coast this morning as a strong upper low intensifies over the Ohio Valley and Mid Atlantic.

I’ve been discussing for several weeks now that a major change in the pattern is upon the Mid Atlantic and much of the eastern two-thirds of the nation.  This storm off the New England coast will eventually lead to a negative NAO pattern that will eventually lock cold air into the eastern third of the nation and support the reposition of the trough over the Rockies towards the Mississippi Valley.

Through today, periods of light to moderate rain can be expected as the upper low continues to intensifys

over the Philadelphia and New York City metropolitan areas.  The 850 MB freezing line will continue to march east as temperatures fall through the day.  The colder air will allow for some snow to mix in with the rain at times, but no accumulations are expected except for the highest elevations.  Overall, this storm is generally a rain producer.

As cold air continues to build into the coast, the mix of rain and snow showers will continue through the evening hours.  However, high pressure over the Mississippi Valley will begin to take hold by early tomorrow morning and a moderation in temperatures will begin.

The high pressure system will remain in control through the weekend with pleasant conditions and near to slightly above normal temperatures.  Skies will have scattered clouds and winds will generally remain light.

High pressure will give way on Monday as a cold front approaches.  The GFS is more aggressive with the timing of the cold front that the ECWMF.  I modified the timing of the ECMWF slightly and expect the cold front to move through on late Monday night into Tuesday morning with widespread showers mixing with snow as the cold front exits.  While Monday will be very warm with many locations in the 50’s for highs, the exact opposite can be expected on Tuesday as temperatures struggle to break out of the 40’s and 30’s.

High pressure will briefly take hold on Wednesday with dry conditions and scattered clouds.  The brunt of the cold air with the previous cold front will be focused towards the Plains and Great Lakes, however temperatures will still average below normal.  Meanwhile, the cold front will be stalled along the Gulf Coast.  A strong disturbance will interact with the boundary and form an area of low pressure over the Southeast.  There is some question with the track of the low as to whether the low move over the New Jersey coast or coastal waters, but the lack of Polar/Arctic air ahead of this storm pretty much assures most locations can expect rain from this second storm.  This is step down number two though, as this low pressure enhances the negative NAO pattern and forces the brunt of the cold air towards the East coast on Thursday.

By next Friday, temperatures will average well below normal and the threat of snow will be in the air.  The pattern will then be set up for a third potential storm and final step down into the winter pattern by around December 10th.  The state of the negative NAO at that time along with a very active Sub Tropical and Polar jet stream suggest that a storm is possible by this time period and the resulting precipitation type from such a storm would be more frozen than liquid.

Extended Thoughts:

I’m becoming concerned that I may bust on the idea of a moderation for mid December given the data I’m looking at.  The idea was based on the MJO going into a neutral position and thus resetting the overall pattern, then due to the warming forces of the stratosphere, reemerge in stage 7 or 8.  The reality is that the MJO continues to truck along into Stage 6, supporting the pattern change that is on going.  If one is to take the trends of the MJO over the past several weeks, this wave will reach stage 7, which is favorable to El Nino conditions.  IF that is the case, then no moderation will unfold and instead the cold pattern will lock in by mid December.  I bolded the if here because a winter pattern locking in by mid December is very rare and if that is the case than this winter may end up being more impressive than I thought in my forecasts.

Meanwhile, the stratospheric warming continues to impress.  I have the 30 MB temperatures to the left, but all levels from 10 MB to 70 MB all show warming well above normal for this time of year, producing record breaking levels.  There is no hint of a significant decline in temperatures at these levels, strongly suggesting that blocking at higher latitudes will be strongly supported.  The only question to me is where will the blocking set up.  The latest observations from the Berlin Stratospheric research group has the strongest warming over eastern Asia, the northern Pacific, and North America; which strongly supports the development of a sustained negative EPO, positive PNA, negative NAO pattern into much of January.  The data is all pointing in the same direction at this point and I don’t see any support for a warm pattern at all.  Get ready for a bumpy ride!

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